Electron gun, charged particle gun, and charged particle beam apparatus using electron gun and charged particle gun

Abstract

The purpose of the present invention is to provide a charged particle gun using merely an electrostatic lens, said charged particle gun being relatively small and having less aberration, and to provide a field emission-type charged particle gun having high luminance even with a high current. This charged particle gun has: a charged particle source; an acceleration electrode that accelerates charged particles emitted from the charged particle source; a control electrode, which is disposed further toward the charged particle source side than the acceleration electrode, and which has a larger aperture diameter than the aperture diameter of the acceleration electrode; and a control unit that controls, on the basis of a potential applied to the acceleration electrode, a potential to be applied to the control electrode.

The invention claimed is: 
     
       1. An electron gun comprising:
 a needle-like electron source acting as a field emission type electron source; an acceleration electrode to accelerate an electron emitted from the electron source; 
 a control electrode disposed nearer to a side of the electron source than to a side of the acceleration electrode and having an aperture diameter larger than an aperture diameter of the acceleration electrode; and 
 a control section to control a potential applied to the control electrode based on a potential applied to the acceleration electrode. 
 
     
     
       2. The electron gun according to  claim 1 , wherein provided that the aperture diameter of the acceleration electrode is defined as D and a distance between the electron source and the acceleration electrode is defined as L, a fraction of D to L is expressed with D/L<1. 
     
     
       3. The electron gun according to  claim 2 , wherein the distance between the electron source and the acceleration electrode is defined as 6 mm<L<20 mm. 
     
     
       4. The electron gun according to  claim 1 , wherein the electron gun is of Cold (Cathode) Field Emission (CFE) type. 
     
     
       5. The electron gun according to  claim 3 , wherein the electron gun is provided with two or more pieces of control electrodes. 
     
     
       6. The electron gun according to  claim 3 , wherein a drawing electrode is provided between the acceleration electrode and the control electrode. 
     
     
       7. The electron gun according to  claim 5 , wherein the electron gun is provided with a control mechanism to switch over electrodes in use according to an acceleration voltage of the electron. 
     
     
       8. A charged particle beam apparatus employing the electron gun according to  claim 1 , the apparatus comprising at least one or more pieces of one of electrostatic and magnetic field lenses; a sample stage on which an observation sample is placed; and a detector to detect at least one of a reflected electron and a secondary electron, wherein the sample is observed or analyzed by the electron beam. 
     
     
       9. The charged particle beam apparatus according to  claim 8  provided with an electron optical system employing one piece of one of electrostatic and magnetic field lenses. 
     
     
       10. The charged particle beam apparatus according to  claim 8 , wherein an outer diameter size of one of the electron gun and an objective lens is 200 mm or smaller. 
     
     
       11. The charged particle beam apparatus according to  claim 8  provided with a function to observe the sample employing the electron beam with a lower acceleration, in which the acceleration voltage of the electron ranges from 0.1 to 3 kV. 
     
     
       12. A charged particle gun comprising:
 a charged particle source; an acceleration electrode to accelerate a charged particle emitted from the charged particle source; 
 a control electrode disposed nearer to a side of the charged particle source than to a side of the acceleration electrode and having a larger aperture diameter than an aperture diameter of the acceleration electrode; and 
 a control section to control a potential applied to the control electrode based on a potential applied to the acceleration electrode. 
 
     
     
       13. A charged particle beam apparatus employing the charged particle gun according to  claim 12 , the apparatus comprising:
 a sample stage on which an observation sample is placed; 
 an objective lens to focus and irradiate the charged particle beam onto the sample; and 
 a detector to detect a secondary electron, 
 wherein the sample is observed or analyzed by the charged particle beam. 
 
     
     
       14. The charged particle beam apparatus according to  claim 13 , wherein the charged particle drawn from the charged particle source are decelerated for use. 
     
     
       15. A charged particle gun comprising:
 a charged particle source; 
 an acceleration electrode to accelerate a charged particle emitted from the charged particle source; 
 a control electrode disposed nearer to a side of the charged particle source than to a side of the acceleration electrode; and 
 a control section to control a potential applied to the control electrode based on a potential applied to the acceleration electrode, wherein the control section applies a control voltage to enhance an electric field at a tip end of the charged particle source to the control electrode when an acceleration voltage of the acceleration electrode is low whereas applying a control voltage to suppress the electric field at the tip end of the charged particle source to the control electrode when the acceleration voltage is high.